Hybrid extruded mixed zeolite catalysts for synthesis of light olefins

ABSTRACT

A catalyst for converting dimethyl ether into light olefins, including ethylene and propylene. The catalyst comprises a mixture of two zeolites, ZSM-5 and ZSM-35, intimately mixed and kept in close proximity in a porous extruded binder system. The resulting combination of zeolites demonstrates a synergistic effect with respect to the conversion of the dimethyl ether and has improved resistance to deactivation due to carbon and coke formation than the individual zeolites alone when operating in this reaction. The catalyst is used to produce ethylene and propylene from a feed mixture containing methanol, dimethyl ether and water.

This application is a divisional of application Ser. No. 15/481,896,filed Apr. 7, 2017, now U.S. Pat. No. 10,406,511, which claims prioritybased on provisional application Ser. No. 62/320,907, filed Apr. 11,2016, the contents of which are incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to the composition, manufacture, and use of newcatalysts that have improved resistance to coke formation and extendedcatalytic activity for producing light olefins from oxygen-containingorganic materials that are obtained from sustainable and fossilresources.

Description of Related Art

-   -   Light olefins such as ethylene and propylene are produced as        by-products in gasoline production and/or by steam cracking        processes, including steam cracking of light alkanes. If a        refinery produces significant amounts of aromatic products,        however, light olefins, such as ethylene and propylene, to        satisfy demand can be produced.    -   Moreover, in the context of fossil fuel resources and the        progressive depletion of oil reserves, alternative and novel        routes for production of light olefins from alternative        feedstock sources become increasingly important.    -   Methanol is a building block molecule, also known as a platform        chemical that can be used in different applications such the        manufacture of formaldehyde according to EP2192102, U.S. Pat.        No. 3,987,107, EP0988269, EP1062195; or gasoline manufacture        according to WO 2014/063758, U.S. Pat. No. 9,028,567; or        Dimethyl ether (DME) production according to U.S. Pat. No.        6,924,399 and US2012/0220804.    -   Methanol can be used to produce light olefins in a methanol to        olefin process. The methanol to gasoline (MTG) technology was        developed by Mobil Oil in the 1970's. This technology used        mordenite framework inverted, or MFI, type zeolites as        catalysts, but it was not until the development of SAPO-34 and        similar SAPO (aluminophosphate or zeotyp) catalysts, that        methanol to olefin (MTO) conversion became highly selective to        light olefins. The mechanism of such processes has been studied        widely and a number of postulates have been presented.

Dimethyl ether is a key intermediate for producing light olefins frommethanol. The dimethyl ether is formed by a methanol dehydrationreaction.2CH₃OH═CH₃OCH₃+H₂O  (1)

Reaction 1 shows the dehydration reaction which proceeds as anequilibrium reaction in which maximum conversion of the methanol isabout 80%. Unconverted methanol can be separated from the reactionproducts, such as water, and then recirculated in the dehydrationreactor, or used as an oxygenate molecule in the feed for the synthesisof light olefins herein described.

There are a number examples of processes that use methanol as afeedstock for synthesizing light olefins. These are described inUS2005/025236, WO2013/034678, WO2004/056944 and US 2003/0078463.

US2005/025236 describes a process for the production of light olefinsfrom methanol and optionally syngas through a dimethyl etherintermediate. The process converts methanol and or syngas into dimethylether and water in the presence of acidic γ-alumina, a modifiedmordenite, zeolite, a ZSM-5 zeolite, sulfonic acid ion exchange resinand a perfluorinated sulfonic acid ionomer catalyst or other catalystand then in a second step converting the dimethyl ether to light olefinand water in the presence of a second catalyst optionally comprising amolecular sieve or zeotyp and zeolite selected from the group consistingof SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31,SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44,SAPO-47, SAPO-56, ZSM-5, metal containing forms thereof, intergrownforms thereof, AEI zeolite/chabazite (CHA) zeolite intergrowths, andmixtures thereof.

WO2013/034678 describes a methanol to olefin process in which a feedconsisting of methanol and ethanol is reacted over a ZSM-5 zeolitecatalyst and is converted to a light olefin product containing ethyleneand propylene.

WO2004056944 describes a process for producing propylene and ethylenerich mixtures from olefinic hydrocarbon streams and the relevantcatalytic systems used.

U.S. Pat. No. 7,230,151, granted to ExxonMobil Chemical Patents Inc.,describes a two catalyst process for making olefins, particularlyethylene and propylene, from an oxygenate feed. The process uses two ormore catalysts with the first catalyst containing ZSM-5 and a secondcatalyst containing ZSM-22, ZSM-23, ZSM-35, ZSM-48, and mixturesthereof.

Al-Dughaither et al. (H. de L. Abdullah S. Al-Dughaither, Neat dimethylether conversion to olefins (DTO) over HZSM-5: Effect of SiO₂/Al₂O₃ onporosity, surface chemistry, and reactivity, Fuel. 138 (2014) 52-64.)stress the many advantages of using DME instead of methanol forsynthesis light olefins. These advantages lead the synthesis to beeconomical if the DME is produced directly from the syngas (lowerequipment cost) and also reduce thermodynamic constraints, lowering theH₂/CO molar ratio to close to 1 for the direct synthesis of DME whilemethanol synthesis operates usually at a ratio above 2.

Catalysts used for the synthesis of light olefins are zeolite basedcatalysts. Several zeolites suitable for catalyzing the production oflight olefins are ZSM-5, ZSM-35, and MOR. ZSM-35 is also interchangeablyreferred to as FER as in ferrierite.

Coke formation (a main cause of deactivation) within the catalyst hasbeen identified as a significant drawback, particularly with ZSM-5zeolite. ZSM-5 for example has a short catalyst operating life of about600 h before catalytic activity is reduced to an extent that it makesthe catalyst unusable. The short life is a result of loss of catalyticactivity with time due to coke formation. Carbon as coke is formed onthe surface and within the pore structure of the zeolite catalyst and isone of the main causes for the loss of catalytic activity as cokeformation results in a progressive loss of catalytic activity andprogressive deactivation of the zeolite catalyst with time. Anothernon-limiting example of coke formation is the deposit of aromatic and/orpolyromantic molecules within the pores of the catalyst. For example,the formation of coke within the pores of the SAPO-34 catalyst at about300° C. to about 380° C. may proceed as follows:

In yet another non-limiting embodiment, the formation of coke within thepores of a catalyst may proceed according to the following mechanism:

The coking process and coke formation are reversible. Catalyst activitycan be recovered by regenerating the catalyst using any number oftechniques already described in the prior art. The need to regeneratethe catalyst reduces the efficiency of the process and adds complexityto the process.

For example, assuming that a process plant annual operating time is inthe order of 8000 hours and the catalyst has an average of 600 hours ofuseful catalytic life, the catalyst would require regeneration or wouldneed to be replaced about 13 times during this operating time period inorder to maintain proper production rates or activity of the catalyst.The rate of catalyst deactivation could be prevented or decreased if itwere possible to reduce the rate of formation of the carbon or coke.This in turn would reduce the number of times or frequency by which thecatalyst would have to be replaced or regenerated. This leads to animprovement in process efficiency and economic advantages by reducingcosts and increasing profitability.

The effects of catalyst deactivation and process requirements formaintaining a steady light olefin production rate can be addressed inseveral ways. One way of achieving a steady production is to use two orthree fixed bed reactors in parallel and cycle their operation with oneor two of the reactors producing olefin, and the remaining reactors areplaced in standby or regeneration mode.

Alternatively, a fluidized bed reactor with a catalyst regenerationsection, similar to a Fluid Catalytic Cracking (FCC) reactor can be usedto regenerate a fraction of the catalyst while the remaining fraction isused to produce olefin.

Catalyst regeneration techniques are employed to remove the coke,although it is not necessary to remove all of the coke formed in and onthe catalyst because it is known that small amounts of residual coke canenhance catalyst performance. It is believed that complete removal ofcoke can also lead to degradation of the zeolite (Michel Guisnet andFernando Ramôa Ribeiro in Deactivation and Regeneration of zeolitecatalysts, Catalytic Science Series, Vol 9, 2011, Imperial CollegePress).

It is also known that water has an effect on the kinetics of cokeformation. Water introduced into the reactor with methanol and/ordimethyl ether, DME, reduces coke formation and as a result increasesthe useful life of the catalyst. Water blocks strong acid sites that areactive for oligomerization, H-transfer and cyclization reactions (A GMarchi and G F Froment Catalytic conversion of methanol to light alkeneson SAPO molecular sieves, Applied Catalysis, 71 p.117)

The mechanism referred to as “hydrocarbon pool” and more recentlyrenamed “dual cycle mechanism”, attempts to explain the selectively tolight olefins synthesis. This is described in the literature (M.Bjorgen, S. Svelle, F. Joensen, J. Nerlov, S. Kolboe, F. Bonino, L.Palumbo, S. Bordiga, and U. Olsbye, Journal of Catalysis, 249 (2007)195-207). The mechanism involves the formation of methylbenzeneintermediates at the catalyst active site during ethylene formation.Olefin methylation and cracking is thought to lead to the formation ofhigher olefins. Aromatic intermediates and higher molecular weightmolecules formed in this mechanism also lead to saturated hydrocarbonand coke formation.

The ideal catalysts for methanol to olefin production would be one thatproduces little coke when used. The ideal catalyst for light olefinssynthesis, assuming equal pore structure effect or shape selectivity,would be one that does not form coke and in which the methylbenzeneintermediate formation rates are unaffected by high selectively towardsthe desired light olefins, i.e., propylene or ethylene or mixture ofpropylene and ethylene.

There is a need for a catalyst that can be used for the production ofolefins from methanol and dimethyl ether where the catalyst has areduced rate of coke or carbon formation. The invention described hereinis a catalyst that addresses this requirement. Such a catalyst wouldreduce the frequency with which the catalyst needs to be regenerated. Anadditional advantage of the invention is that in a surprising andunexpected manner the catalyst has improved selectivity to light olefinproduction. Another advantage of the catalyst described herein is thatthe amount of coke produced is reduced when compared to using ZSM-5 andZSM-35 catalysts alone under the same operating conditions.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, there is provideda composition comprising a mixture of two zeolite catalysts. Such acomposition has previously unrecognized performance advantages overexisting catalysts with respect to coke formation rate, selectivitytowards ethylene and propylene production, and catalyst life.

In a non-limiting embodiment, one or more zeolites are combined to forma mixture that has improved capability of catalyzing the production ofolefins from a feed comprising dimethyl ether, or methanol, and/or amethanol and dimethyl ether mixture.

In another non-limiting embodiment, one or more zeolites are combined toform a mixture that has improved capabilities of catalyzing theproduction of olefins from oxygenated hydrocarbons.

An object of the present invention is to provide a more robust catalystcomposition having a reduced tendency to form coke when used for lightolefin synthesis. The light olefins which may be synthesized include,but are not limited to, ethylene, propylene, and mixtures thereof.

A further object of the present invention is to use a mixture of lightorganic oxygenated compounds to synthesize light olefins.

Another object of the present invention is to provide a catalyst thathas increased catalytic activity for producing light olefins frommethanol.

Yet another object of the present invention is to provide a catalystthat comprises two or more zeolites that together have a synergic effectand reduce the rate of coke formation.

Another object of the present invention is to provide a catalyst thatcomprises two or more zeolites that together have a synergistic effectand reduce the rate of coke formation while producing predominantly morepropylene than ethylene.

A further object of the present invention is to provide a catalyst thatcomprises two zeolites that together have a synergistic effect andreduce the rate of catalyst deactivation when used for convertingmethanol to olefins.

Another object of the present invention is to provide a catalyst thatcomprises two zeolites that together have a synergistic effect andreduce the rate of catalyst deactivation when used for convertingmethanol and dimethyl ether to olefins or light olefins.

Another object of the present invention is to provide a catalyst thatcomprises two or more zeolites that together produce olefins wherein theolefins are ethylene and propylene.

Another object of the invention is to provide a catalyst that comprisestwo or more zeolites that together have a synergistic effect on theconversion of dimethyl ether to olefins.

Another object of the invention is to provide a catalyst that comprisestwo or more zeolites that together have a synergistic effect on theconversion of dimethyl ether to olefins and increases the conversion toabout 90%.

In a non-limiting embodiment, the catalyst comprises ZSM-5 and ZSM-35.

An object of the present invention is to produce a catalyst that retainscatalytic activity for a longer period than a single zeolite, such as,for example, a longer period than ZSM-5 alone, and thus reduces thenumber of catalyst regenerations.

Another object of the present invention is to produce an extrudedcatalyst containing two zeolites that when combined have improvedcatalytic properties for the conversion of dimethyl ether to lightolefins.

Another object of the present invention is to produce an extrudedcatalyst containing two zeolites that when combined have improvedcatalytic properties for the conversion of methanol and dimethyl etherto light olefins.

Another object of the present invention is to produce an extrudedcatalyst or a catalyst extrudate, containing two zeolites that whencombined have improved catalytic properties for the conversion ofmethanol, water, and dimethyl ether to light olefins.

In a non-limiting embodiment, the composition further comprises abinder, and the zeolite catalysts are mixed with a binder to form anextruded catalyst or catalyst extrudate. In a non-limiting embodiment,the binder is selected from the group consisting of silicas, includingcolloidal silicas and amorphous silicas, clays, alumina, includingamorphous alumina, and mixtures thereof.

Another object of the present invention is to provide a catalyst orcatalyst extrudate with a high mesoporosity.

In another non-limiting embodiment of the invention, the extrusionprocess retains the high mesoporosity of the included zeolitestructures.

In another non-limiting embodiment, the zeolite comprises a mixture ofZSM-5 and ZSM-35.

In another non-limiting embodiment, the zeolite comprises a mixture ofMFI and ZSM-35 zeolite.

In a further non-limiting embodiment, the zeolite comprises a mixture ofZSM-5 and FER zeolite.

In yet another non-limiting embodiment, the zeolite comprises a mixtureof MFI and FER zeolite.

In another non-limiting embodiment, the catalyst extrudate is formedusing a binder.

In another non-limiting embodiment, the binder is amorphous silica.

In another non-limiting embodiment, extrudate is cross-linked using anammonium nitrate salt.

In another non-limiting embodiment, the extruded catalyst is preparedfrom a silica solution.

In further non-limiting embodiment, the extruded catalyst is preparedfrom a silica sol with particle sizes of about 12 nm.

In another non-limiting embodiment, the binder is an inorganic binder ofamorphous silica or amorphous alumina or a combination of both.

In a non-limiting embodiment, the binder is silica.

In a non-limiting embodiment, the binder is silica from colloidalsilica.

In a non-limiting embodiment, the binder is amorphous silica.

In a non-limiting embodiment, the binder is clay.

In a non-limiting embodiment, the binder is amorphous alumina.

In another non-limiting embodiment, the binder is a mixture of one ormore of silica, amorphous silica, clay, and amorphous alumina.

In another non-limiting embodiment, the binder is an inert binder or aninorganic binder which does not have catalytic activity.

In yet another non-limiting embodiment, the inert binder is an inorganicbinder that includes one or more of alumina, silica, amorphous silica,amorphous alumina or a binder derived from colloidal silica.

In a non-limiting embodiment, the binder imparts additional catalyticactivity to the catalyst mixture.

Another object of the present invention is to provide a process toproduce an extruded catalyst containing at least two zeolites that whencombined have improved catalytic properties for the conversion ofdimethyl ether and water into light olefins.

Another object of the present invention is to provide a catalyst thathas improved selectivity towards the formation of ethylene.

Another object of the present invention is to provide a catalyst thathas improved selectivity towards the formation of propylene.

Another object of the present invention is to provide a catalyst thathas improved selectivity towards the formation of ethylene andpropylene.

Yet another object of the present invention is to produce a catalyst forproducing light olefins from dimethyl ether.

A further object of the present invention is to produce a catalyst forproducing light olefins from a mixture of dimethyl ether and water.

Another object of the present invention is to produce a catalyst forproducing light olefins from a reaction mixture of dimethyl ether,water, and methanol.

Another object of the present invention is to provide a method forproducing a catalyst that has a reduced tendency to deactivate duringthe synthesis of light olefins from dimethyl ether, water, and methanol.

Yet another object of the present invention is to provide a method forproducing a catalyst that has a reduced tendency to deactivate as aresult of coke formation during the synthesis of light olefins fromdimethyl ether, water, and methanol.

Another object of the present invention is to provide a method forproducing a catalyst that has improved performance and reduced tendencyto deactivate as a result of coke formation and an increased resistanceto coke formation during the synthesis of light olefins from dimethylether, water, and methanol.

Another object of the present invention is to provide a method for usingthe catalyst for the conversion of dimethyl ether into light olefins.

Another object of the present invention is to provide a catalyst thathas an increased resistance to deactivation.

Another object of the present invention is to provide a catalystcomposition that comprises a mixture of ZSM-5 and ZSM-35 zeolites.

Another object of the present invention is to provide a catalystcomposition that comprises a mixture of ZSM-5 and ZSM-35 zeolite formedinto an extrusion.

Yet another object of the present invention is to provide a process formanufacturing the extruded catalyst.

Another object of the present invention is to provide a catalyst mixturethat reduces the amount of coke formation from about 23 to about 46% theamount of coke produced if ZSM-5 were used alone and under similaroperating conditions.

Another object of the present invention is to provide a more robustcatalyst that is resistant to coke formation, for light olefin synthesisfrom a mixture of dimethyl ether, water, and methanol.

In a non-limiting embodiment, the catalyst used for light olefinsynthesis from methanol, dimethyl ether and water comprises ZSM-5 andZSM-35 zeolites, and a binder.

In another non-limiting embodiment, the catalyst used for light olefinsynthesis from methanol, dimethyl ether, and water comprises ZSM-5 andZSM-35 zeolites, and an inert binder.

In a non-limiting embodiment, light olefin(s) is (are) synthesized froma mixture of methanol, dimethyl ether, and water is the presence of acatalyst that comprises ZSM-5 and ZSM-35 zeolites and a binder.

In another non-limiting embodiment, light olefin(s) is (are) synthesizedfrom a mixture of methanol, dimethyl ether, and water is the presence ofa catalyst that comprises of ZSM-5 and ZSM-35 zeolites and an inertbinder.

In a non-limiting embodiment, ZSM-5 zeolite is present in an amount offrom about 10 wt. % to about 95 wt. % of the total amount of zeolite inthe composition.

In a non-limiting embodiment, ZSM-5 is present in an amount of fromabout 10 wt. % to about 90 wt % of the total amount of zeolite in thecomposition.

In another non-limiting embodiment, ZSM-5 is present in an amount offrom about 40 wt. % to about 90 wt. % of the total amount of zeolite inthe composition, in a further non-limiting embodiment, ZSM-5 is presentin an amount of from about 55 wt. % to about 85 wt. % of the totalamount of zeolite in the composition.

In a non-limiting embodiment, ZSM-35 is present in an amount of fromabout 5 wt. % to about 90 wt. % of the total amount of zeolite in thecomposition.

In another non-limiting embodiment, ZSM-35 is present in an amount offrom about 10 wt. % to about 90 wt. % of the total amount of zeolite insaid composition.

In another non-limiting embodiment, ZSM-35 is present in an amount offrom about 10 wt. % to about 60 wt. % of the total amount of zeolite inthe composition.

In yet another non-limiting embodiment, ZSM-35 is present in an amountof from about 15 wt % to about 45 wt. % of the total amount of zeolitein the composition.

In a non-limiting embodiment, the catalyst used in the synthesis oflight olefins includes ZSM-5 dispersed in a binder.

In a non-limiting embodiment, the catalyst used in the synthesis oflight olefins includes at least ZSM-35 dispersed in a binder.

In another non-limiting embodiment, the catalyst used in the synthesisof light olefins includes at least ZSM-5 and ZSM-35 dispersed in abinder.

In a non-limiting embodiment, the catalyst comprises a mixture ofextruded ZSM-5 and ZSM-35 having a high mesoporosity. The catalystmixture provides a reduction in the amount of carbon formation by about23 to 46% compared to ZSM-5 based zeolite alone. The catalyst alsoreduces the rate of coke formation by 23 to 46% in comparison to ZSM-5.

In a non-limiting embodiment of the invention the molar percent ofethylene product to the total amount of ethylene and propylene producedis about 23% while conversely the molar percent of propylene to thetotal amount of ethylene and propylene produced is about 77%.

In a non-limiting embodiment, one or more of the dimethyl ether andmethanol used for the synthesis of olefins are obtained from renewableor sustainable sources.

In a non-limiting embodiment, renewable sources of syngas for producingthe methanol or dimethyl ether include agricultural crop residues andwaste, urban municipal waste, industrial organic residues, andconstruction and demolition waste.

In a non-limiting embodiment, renewable sources of syngas which may beused to produce the methanol or dimethyl ether can be biomass, municipalwaste, construction wastes, forest waste residues, or any othersustainable source of carbon containing material.

In a non-limiting embodiment, oxygenated hydrocarbons comprise the feedto the reactor.

The oxygenated hydrocarbons include methanol and dimethyl ether.

In a non-limiting embodiment, the ZSM-5 zeolite is dispersed in a binderhaving a mesoporous volume of at least 0.07 cm³/g-zeolite and may begreater than 0.10 cm³/g-zeolite.

In a non-limiting embodiment, the ZSM-35 zeolite is dispersed in abinder having a mesoporous volume of at least 0.03 cm³/g-zeolite and maybe greater than 0.10 cm³/g-zeolite.

In a non-limiting embodiment, is a mixture of ZSM-5 and ZSM-35 isdispersed in a binder and has a mesoporous volume of at least 0.03cm³/g-zeolite and may be greater than 0.10 cm³/g-zeolite.

In a non-limiting embodiment, a mixture of ZSM-5 and ZSM-35 is dispersedin a binder to give an average pore diameter between 9.1 and 9.3 nm.

In a non-limiting embodiment, a mixture of ZSM-5 and ZSM-35 is dispersedin a binder and has a specific surface area between about 324 to 410m²/g catalyst.

In a non-limiting embodiment, the mixed zeolite catalyst, which may bein extruded form, is subjected to a cross-linking process by contactingthe catalyst with ammonium nitrate, and then the catalyst is calcined.

DETAILED DESCRIPTION OF THE INVENTION

The following terms are defined below:

DME—Dimethyl ether.

IMPCA—International Methanol Producers and Consumers Association.

FER—a group of zeolite materials comprising forms of ZSM-35 zeolite.

Mordenite Framework Inverted, or MFI—a group of zeolite materialscomprising forms of ZSM-5 zeolite.

WHSV—Weight Hourly Space Velocity as the weight of feed per hour perunit weight of catalyst loaded in the reactor.

medium pore size zeolites—a group of zeolites classified on the size ofthe pore structure, which includes ZSM-5 and ZSM-35.

Renewable material used for producing methanol and dimethyl ether isgasified by any known means such as the methods and processes describedin U.S. Pat. Nos. 8,137,655 and 8,192,647. Synthesis gas produced in thegasification process is used for the methanol synthesis. The productionof methanol from syngas is carried out at a temperature in the range ofabout 200 to 300° C. and a pressure range of about 20 to 100 bar over acatalyst including mixed oxides of copper, zinc and chromium, and copperzinc aluminum oxide catalyst as described in U.S. Pat. No. 3,326,956.

Catalysts used for methanol synthesis are available commercially withdetails of manufacture given in U.S. Pat. No. 3,840,478 wherein themanufacture of copper oxide-zinc oxide and chromium oxide catalysts formethanol synthesis are described.

The synthesis gas used for manufacturing the methanol can also beobtained from any other known method for producing syngas, such as'steam, partial oxidation, or autothermal reforming of hydrocarbons orother carbon sources including natural gas.

Reactant dimethyl ether, (DME), is produced by dehydrating methanol overcommercially available acid catalyst. It is not necessary for themethanol used for dimethyl ether synthesis to be pure. Methanol with apurity of 99.85% as defined by the IMPCA reference specification formethanol, can be used or a less pure methanol such as 70-80% w/w ofmethanol with a 20-30% w/w water content can be used as the methanolsource for the dehydration reaction.

Synthesis gas produced from renewable materials through gasificationtechnology, can be used to synthesize dimethyl ether directly. Thisprocess is referred to as the “one step dimethyl ether productionprocess”. Methods for direct synthesis of dimethyl ether from synthesisgas are described in EP2028173 and US2015/0018582.

EP2028173 describes a catalytic process for the conversion of syngasconsisting of carbon monoxide, carbon dioxide and hydrogen to dimethylether in a catalytic process comprising contacting a stream of synthesisgas comprising carbon dioxide in a first dimethyl ether synthesis stepwith one or more catalysts active in the formation of methanol and thedehydration of methanol to dimethyl ether to produce a productcomprising dimethyl ether, methanol, carbon dioxide and unconvertedsynthesis gas, and washing the product mixture comprising carbon dioxideand unconverted synthesis gas in a scrubbing zone with a liquid solvent.

The solid catalyst extrudate is used for the production of a productcomprising light olefins from a feed mixture that contains one or moreof methanol and dimethyl ether and optionally water at reactionconditions that produce light olefins. The solid catalyst extruded formcomprises a mixture of two different zeolites and an inert binder suchthat the combination of zeolites results in an improved and positivesynergistic effect on catalytic performance and a reduced rate of cokeformation that otherwise would not be realized if the individual zeolitesimply were mixed or layered in a reactor and not in intimate contactwithin a single catalyst form and bound by a porous inert binder.

In a non-limiting aspect of this invention, light olefins aresynthesized from a mixture of dimethyl ether, water, and methanol. Thereaction is carried out at a temperature of from about 200 to 500° C.and at atmospheric or higher pressures.

The reaction is carried out in a reactor that is a catalytic fixed bed,a fluidized bed, a tubular reactor, or other type of reactor into whichthe catalyst can be placed.

In a non-limiting embodiment, the catalyst used for the synthesis oflight olefins from dimethyl ether and methanol and water mixture,comprises ZSM-5 and ZSM-35 and a binder.

In a non-limiting embodiment, the catalyst used for the synthesis oflight olefins is in an extruded form.

A another non-limiting embodiment, is that the catalyst used for thesynthesis of light olefins is pelletized.

In yet another non-limiting embodiment, the extruded catalyst hereindescribed that is used for the synthesis of light olefins is in the formof small solid cylinders or spheres.

In another non-limiting embodiment, one form of the ZSM-5 zeolitedispersed in the binder for light olefins synthesis is an MFI typezeolite as described in the “Atlas of Zeolite Framework types”, D HOlson, Ch. Baerlocher et al., 6th edition, 2007, wherein such atlasstates that ZSM-5 zeolites are tridimensional zeolites with poreaperture dimensions of 5.1×5.7 Å and 5.3×5.6 Å.

In another non-limiting embodiment, one form of the ZSM-35 zeolitedispersed in the binder has specific properties and characteristics forolefin synthesis, and is an MFI type zeolite described in the “Atlas ofZeolite Framework types”, DH Olson, Ch. Baerlocher et al., 6th edition,2007. ZSM-35 is a tridimensional zeolite with pore aperture dimension of5.5×4.3 Å and 4.8×3.4 Å.

Both ZSM-5 and ZSM-35 are in a class of zeolites that is referred to asmedium pore size zeolites.

The zeolite powder materials are mixed in suitable proportions as hereindescribed and mixed with a binder. The resulting mixture is then formedinto an extrudate which is then shaped before being dried and calcinedto give the calcined catalyst. The calcined catalyst is then crosslinked by adding ammonium nitrate, drying and then calcined a secondtime. The resulting extruded form is the cross-linked catalyst and alsois the activated catalyst. The ammonium nitrate and calcination stepsactivate the catalyst.

Mixing the zeolites in this way and forming them into a single catalystextrudate results in a hybrid catalyst which also can be referred to asa hybrid zeolite catalyst.

The hybrid catalyst is produced, in a non-limiting embodiment, by mixingpowder forms of the zeolites as herein described, followed by dispersingthe mixture of zeolite powders in water and then adding colloidal silicato form a first dispersion, and adding hydroxyethylcellulose to themixture to form a first plastic paste. The paste then is passed throughan extrusion die and cut to give uniformly sized cylindrical catalystforms. The cylindrical catalyst forms are allowed to dry at roomtemperature before being calcined in an oven to about 550° C. to providea calcined catalyst.

The calcined catalyst is used in a reactor for the conversion ofdimethyl ether to olefins as described herein.

The catalyst produced in this manner was found to have improvedperformance with respect to carbon formation. The catalyst showed animproved capacity for reduced coke formation with one combination ofZSM-5 and ZSM-35 presenting surprising results that would not have beenexpected.

In a non-limiting embodiment of the invention, the performance of thecatalyst and its selectivity towards producing olefins was measured in afixed catalytic bed. Oxygenated hydrocarbons such as methanol anddimethyl ether were used in the experiments for testing the catalysts.Methanol, dimethyl ether and water were mixed in a fixed-bed reactor attemperatures from about 400 to about 515° C. with Weight Hourly SpaceVelocities in the range of from about 15 to about 50h⁻¹. The catalystwas found to have exhibited high conversion and selectivity toward lightolefins while demonstrating a reduced susceptibility to the loss ofactivity because of coke and carbon formation.

In a non-limiting embodiment, the water content in the feed to thereactor is from about 25 wt. % to about 60 wt. %.

In another non-limiting embodiment, the water content in the feed to thereactor is from about 30 wt. % to about 40 wt. %.

In a further non-limiting embodiment, the temperature of the reaction inthe reactor is from about 250° C. to about 500° C.

In another non-limiting embodiment, the temperature of the reaction inthe reactor is from about 400° C. to about 500° C.

In a non-limiting embodiment, the gas hourly space velocity is fromabout 15 to about 50 h⁻¹.

EXAMPLES

Embodiments of the present invention are further illustrated by thenon-limiting examples which follow. It is to be understood, however,that the scope of the present invention is not intended to be limitedthereby.

Example 1

Two commercial zeolites, NH₄ ZSM-5 and NH₄ FER, were supplied by ZeolystInternational in powder form. These were used to manufacture a number ofextruded catalysts with varying loadings of zeolite.

The hybrid catalyst extrusions used for testing and demonstrating theperformance of the catalyst were prepared as described below.

An aliquot of each catalyst was weighed in an appropriate proportion soas to give the desired weight ratio for each zeolite in the finalextrusion.

The NH₄ ZSM-5 and NH₄ FER zeolites powder aliquots then were mixedtogether for 10 minutes.

A colloidal silica (W.R. Grace, Ludox™ HS-40) solution then was added tothe zeolite mixture with agitation and the resulting solution was mixedfor a further 10 minutes. The colloidal silica was used as a binder forthe zeolites and adds strength to the resulting extrudate.

Sufficient colloidal silica was added to the mixture so that the dryform of the extrudate would contain 75% (w/w) zeolite and 25% (w/w)silica on a dry basis. For example when using a colloidal silicasolution supplied as a 40% weight solution of silica, 100 g of colloidalsilica solution is added to every 120 g of dry zeolite mixture to give asuspension of zeolite and colloidal silica.

An about 8.5% (w/w) solution hydroxyethylcellulose solution was preparedby dissolving the polymer in deionized water with mixing for 10 minutesor until the solid had dissolved.

The hydroxyethylcellulose adds a degree of plasticity to the unformedextrudate of the catalyst mixture. An optimal liquid/solid relationshipof 0.6 was used and found to be effective.

98 g of the hydroxyethylcellulose solution then was mixed with thezeolite-colloidal silica mixture and mixing continued for at least 20minutes after which time it gave a smooth paste blend.

The hydroxyethylcellulose is added as a temporary binder to bind thesolid particles of the dispersion and form a paste with plasticproperties that allow the paste to be formed and extruded into a stableshape.

The smooth paste blend then was passed through an extrusion die to givecylindrical sticks with a diameter of about 3 to 4 mm and lengths ofabout 10 to 30 cm. The extruded forms then were cut into about 3 to 5 mmlong pellets that were then allowed to dry at room temperature for 24 h.

The dried catalyst pellets then were placed in a calcination oven atroom temperature. The calcination process heated the oven from roomtemperature up to about 550° C. with a heating ramp of 2° C./minute. Thecatalyst then was left to stand in the oven at 550° C. for 3 hours ormore. After this time the calcined catalyst was allowed to cool slowlywith the oven to give the calcined extrudate.

After cooling, a nitrate impregnation and crosslinking process was usedto activate the catalyst. The calcined extrudate so produced was mixedwith a 2M aqueous ammonium nitrate (NH₄NO₃) solution. The solution wasmaintained at 55° C. with 100 ml of nitrate solution added per 10 g ofcalcined extrudate used. The resulting nitrate impregnated calcinedextrudate solid material was then left to dry in air for 4 h.

The resulting nitrate impregnated dry calcined extrudate was thencalcined a second time using a similar process to the first. The drynitrated impregnated calcined extrudate was placed in an oven at roomtemperature and heated to a temperature of 550° C. at a rate of 2°C./minute and then allowed to soak at 550° C. for 3 hours. Theextrudates were allowed to cool with the oven and then placed in adesiccator.

This catalyst preparation process herein described produced an activatedsolid, compression resistant catalyst that could be used directly in areactor.

The resulting solid calcined catalyst particles were removed from theoven and allowed to cool in a desiccator in a nitrogen purgedatmosphere. The catalyst particles were uniform in shape and size withsufficient strength to resist compression.

The calcined cross-linked catalyst form was then allowed to cool slowlywith the oven, before being removed and stored in a desiccator untilused

Table 1 shows the composition and combinations of each component andzeolite in the catalyst particles manufactured using this process. Table2 shows the sample identifiers and composition of each of the catalystprepared and the amount of each zeolite used for each on a dry basis ofcalcined catalyst.

TABLE 1 Extrusion sample preparation - material compositions beforedrying. Material Weight g Total Zeolite 187.5 40% Colloidal silica156.25 (Ludox-HS40) Hydroxyethylcellulose 12.75 Water 43.5

TABLE 2 Mixed Zeolite Catalyst Sample Composition - excluding Binder.Weight Percentage Weight Catalyst Zeolite % Zeolite g Name FER ZSM-5 FERZSM-5 100-H-ZSM-5 0 100 0 187.5 Hybrid I 10 90 18.75 168.75 Hybrid II 2080 37.5 150 Hybrid III 40 60 75 112.5 Hybrid IV 60 40 112.5 75 100-H-FER100 0 187.5 0

Example 2

The catalysts produced in Example 1 were analyzed using a number oftechniques to quantify the structure, surface area, and pore sizeswithin the catalyst. This was done to confirm that the pore structurehad not changed significantly during the preparation of the mixedcatalyst extrudate.

Table 3 shows the results obtained in these measurements and a number ofconclusions and observations can be drawn from these data. Thepercentage crystallinity between the pure catalyst and the extruded formof the pure catalyst appears to change in line with the ratio of bindingmaterial and zeolite loading. The binding material, present as silica,would be expected to be present as an amorphous material afterclassification.

TABLE 3 Catalyst Properties and Characterization Results. BET Weigh % N₂Adsorption Surface Zeolite % (cm³/g zeolite) Area PORE SIZE FER ZSM-5Crystallinity V_(micro) V_(meso) m²/g (nm) H-ZSM5 (P) — 10 100 0.12 0.06409.84 5.5 H-ZSM5 (E) — 10 75 0.13 0.14 329.48 9.2 H-FER (P) 10 — 1000.12 0.02 361.8 9.2 H-FER (E) 10 — 75 0.13 0.13 324.33 9.2 Hybrid I (E)1 9 0.13 0.13 324.57 9.24 Hybrid II (E) 2 8 0.13 0.14 329.5 9.22 HybridIII (E) 4 6 0.13 0.14 332 9.27 Hybrid IV (E) 6 4 0.13 0.14 329.5 9.23 E:Extruded, P: Powder

It is surprising to note that after mixing and calcination, thecatalysts all have a pore size that is about 9.2 nm. This remains thecase when 90% of the catalyst is made up of ZSM-5, which has an averagepore size of 5.5 nm before being incorporated in the catalyst extrudate.

The catalyst produced using the method of Example 1 with thecompositions given in Table 4 each were tested in a reactor with variousfeed mixtures containing dimethyl ether, water, and methanol. Themethanol and dimethyl ether to olefin reaction conditions at which eachcatalyst was tested are given in Table 5. The methanol, water, anddimethyl ether feed composition was kept constant in these reactionswhile the reactions were done at atmospheric pressure.

TABLE 4 Mixed Zeolite Catalyst Sample Composition with binder. CatalystWeight Percentage % Weight of component g Name FER ZSM-5 Silica FERZSM-5 Silica 100-H-ZSM-5 0 75 25 0 187.5 62.5 Hybrid I 7.5 67.5 25 18.75168.75 62.5 Hybrid II 15 60 25 37.5 150 62.5 Hybrid III 30 45 25 75112.5 62.5 Hybrid IV 45 30 25 112.5 75 62.5 100-H-FER 75 0 25 187.5 062.5

TABLE 5 Methanol to olefin reaction operating conditions. Feedcomposition (wt. %) Temperature (° C.) WHSV (h⁻¹) MeOH DME Water 400 155 60 35 All reactions were done at atmospheric pressure.

The results for each case were tabulated in Table 6. The samplecontaining 20% HFER and 80% HZSM shows a capability that is surprisingand unexpected relative to the other catalyst compositions. Thisformulation of catalyst demonstrates ability for increased dimethylether conversion, with up to about 90.2% conversion which is asignificant improvement compared to the other catalyst mixtures and thecatalysts containing only a single zeolite. This performance wassurprising and would not and could not have been predicted from the dataobtained for the other mixtures. It is clear the having both zeolitespresent at this ratio has a significant and measurable synergic effecton catalyst performance.

TABLE 6 Product distribution by molar percentage after 350 minutesreaction time on hybrid catalyst mixtures of H-ZSM-5 (HZSM) and H-ZSM-35(HFER). HZSM HFER 10 HFER- 20 HFER- 40 HFER- 60 HFER- (280) (20) 90 HZSM80 HZSM 60 HZSM 40 HZSM Mol % Mol % Mol % Mol % Mol % Mol % C₁-C₄ 0.00.0 0.0 0.0 0.0 0.0 C₂= 13.04 92.98 30.17 16.24 32.49 23.48 C₃= 56.612.05 40.60 53.29 30.69 38.85 C₄= 6.75 0.66 4.29 6.98 6.24 9.06 C₅ ⁺=3.63 1.26 4.33 5.06 5.96 6.52 Paraffin's (C₅ ⁺) 14.34 1.63 14.56 13.2417.30 14.93 Naphtha's (C₅ ⁺) 1.50 0.40 1.04 1.63 1.43 2.07 Aromatics4.13 1.01 5.00 3.56 5.89 5.09 Conversion DME 82.6 34.6 70.7 90.2 71.187.3 after 5 hours Coke (wt. %) 1.48 5.7 1.49 1.14 0.8 1.25

It also is seen that the 20% HFER-80% HZSM catalyst mixture alsoproduces a product mixture that contains about 53.3% propylene, which issignificantly more than any of the other mixtures. The single zeoliteversion of the catalyst is the only catalyst that produces more than53.3% propylene. The 20% HFER-80% HZSM catalyst mixture also producedless aromatic compounds in the product mixture while also not producingthe lowest carbon formation rate of the catalyst tested. This mixturedid have a slower rate of carbon formation than either of the catalystsproduced using only one zeolite. The carbon produced after 5 hours ofoperation was about 1.14 wt. % on the catalyst.

Example 3

The catalysts were tested in a fixed bed stainless steel reactor (2.03cm i.d, length=100 cm). The catalyst samples were conditioned in situ byheating them to 515° C. at a rate of 5° C./minute under nitrogen with aflow of 200 actual milliliters minute measured at laboratory conditions.The catalysts then were kept at to 515° C. for 5 h or more.

The catalyst temperature then was set to the required experimenttemperature, Table 5, and allowed to equilibrate. All the catalystformulations were exposed to a given feed composition for a continuous 5hour periods. Liquid methanol and water was mixed with a metered amountof dimethyl ether. The resulting mixture was then fed into the top ofthe reactor and passed down through the catalyst bed before leaving thereactor.

The hot vapor reaction product vapor mixture leaving the reactor thenwas cooled to 30° C. before liquid and vapor fractions were separatedinto a vapor stream and a liquid stream. Analysis of these streamsshowed that the liquid stream was a mixture of water, and organiccompounds while the vapor stream was a mixture of non-condensablehydrocarbon vapors.

All process runs resulted in 100% conversion of the feed methanol and upto about 90.2% conversion of dimethyl ether, with conversion beingcalculated as the ratio of {the number of moles of feed component lessthe number of feed component in the reaction product} to the number offeed component in the feed.

The conversion of dimethyl ether was between 34.6 and 90.2 wt. %. Hybridcatalyst containing 80 wt. % ZSM and 20 wt. % FER resulted in a dimethylether conversion of about 90.2 wt. %. A hybrid catalyst consisting of 40wt % ZSM and 60 wt. % FER that gave a dimethyl ether conversion of about87.3 wt. %.

The preceding example(s) can be repeated with similar success bysubstituting the various components and configurations for each zeoliteas described herein.

Although the invention has been described in detail with particularreference to a number of embodiments, embodiments can be derived at thatgive the same or similar results. Upon studying this application it willbe possible that those skilled in the art will realize other equivalentvariations and/or modifications. It is intended that the claimscontained in any patent issued on this application cover all suchequivalents. The entire disclosures of all references, applications,patents, and publications cited above are hereby incorporated herein byreference to the same extent as if each patent, patent application, andreference were incorporated individually by reference.

It is to be understood, however, that the scope of the present inventionis not to be limited to the specific embodiments described above. Theinvention may be practiced other than as particularly described, andstill be within the scope of the accompanying claims.

What is claimed is:
 1. A method of producing at least one olefin fromdimethyl ether, comprising: reacting a feed comprising dimethyl etherunder catalytic conversion conditions in the presence of a compositioncomprising at least one catalyst particle, wherein each of said at leastone catalyst particle(s) contains a ZSM-5 zeolite, a ZSM-35 zeolite, anda binder, to produce a product comprising at least one olefin.
 2. Themethod of claim 1 wherein said feed further comprises methanol.
 3. Themethod of claim 2 wherein said feed further comprises water.
 4. Themethod of claim 1 wherein said at least one olefin is ethylene.
 5. Themethod of claim 1 wherein said at least one olefin is propylene.
 6. Themethod of claim 1 wherein said at least one olefin comprises ethyleneand propylene.
 7. The method of claim 1 wherein said ZSM-5 zeolite ispresent in an amount of from about 10 wt. % to about 95 wt. % of thetotal amount of zeolite in said composition.
 8. The method of claim 7wherein said ZSM-5 zeolite is present in an amount of from about 10 wt.% to about 90 wt. % of the total amount of zeolite in said composition.9. The method of claim 8 wherein said ZSM-5 zeolite is present in anamount of from about 40 wt % to about 90 wt. % of the total amount ofzeolite in said composition.
 10. The method of claim 9 wherein saidZSM-5 zeolite is present in an amount of from about 55 wt. % to about 85wt. % of the total amount of zeolite in said composition.
 11. The methodof claim 1 wherein said ZSM-35 zeolite is present in an amount of fromabout 5 wt. % to about 90 wt. % of the total amount of zeolite in saidcomposition.
 12. The method of claim 11 wherein said ZSM-35 zeolite ispresent in an amount of from about 10 wt. % to about 90 wt. % of thetotal amount of zeolite in said composition.
 13. The method of claim 12wherein said ZSM-35 zeolite is present in an amount of from about 10 wt.% to about 60 wt. % of the total amount of zeolite in said composition.14. The method of claim 13 wherein said ZSM-35 zeolite is present in anamount of from about 15 wt. % to about 45 wt. % of the total amount ofzeolite in said composition.
 15. The method of claim 1 wherein saidbinder is selected from the group consisting of silicas, clays,aluminas, and mixtures thereof.
 16. The method of claim 15 wherein saidbinder is a silica.
 17. The method of claim 16 wherein said silica isderived from colloidal silica.
 18. The method of claim 16 wherein saidsilica is an amorphous silica.
 19. The method of claim 15 wherein saidbinder is a clay.
 20. The method of claim 15 wherein said binder is analumina.
 21. The method of claim 20 wherein said alumina is an amorphousalumina.